Vitamin D 3 is activated in the liver and kidney before fully active as a regulator of calcium and phosphorus metabolism at target tissues.Contraindications for vitamin D analogues (Vitamin D2, Vitamin D3, Calcitriol, and Calcidiol): Vitamin D should not be given to patients with hypercalcemia or evidence of vitamin D toxicity. Use of vitamin D in patients with known hypersensitivity to vitamin D (or drugs of the same class) or any of the inactive ingredients is contraindicated.Calcitriol is used in treatment of secondary hyperparathyroidism and resultant metabolic bone disease in patients with moderate to severe chronic renal failure (Ccr 15 to 55 mL/min) not yet on dialysis. The pharmacology action of Calcitriol is that it supply of vitamin D depends mainly on exposure to ultraviolet rays of the sun for conversion of 7-dehydrocholesterol in the skin to vitamin D 3 (cholecalciferol).
Calcitriol is a form of vitamin D that is prescribed to treat and prevent low levels of calcium in the blood of patients whose kidneys or parathyroid glands (glands in the neck that release natural substances to control the amount of calcium in the blood) are not working normally. Low blood levels of calcium may cause bone disease. Calcitriol is in a class of prescription called vitamins. It works by helping the body to use more of the calcium found in foods or supplements.
Calcitriol is produced in the kidneys via 25-Hydroxyvitamin D3 1-alpha-Hydroxylase by conversion from 25-hydroxycholecalciferol (calcidiol). Calcitriol or 1,25-dihydroxycholecalciferol (abbreviated 1,25-(OH)2D3) is the active form of vitamin D found in the body (vitamin D3). Calcitriol is marketed under various trade names including Calcitriol (Roche), Calcijex (Abbott) and Decostriol (Mibe, Jesalis). This is stimulated by a decrease in serum calcium, phosphate (PO43a?’) and parathyroid hormone (PTH) levels. It regulates calcium levels by increasing the absorption of calcium and phosphate from the gastrointestinal tract, increasing calcium and phosphate reabsorption in the kidneys and inhibiting the release of PTH. Calcitriol is also commonly used as a prescription in the treatment of hypocalcemia and osteoporosis.
Indication - Used to treat vitamin D deficiency or insufficiency, refractory rickets (vitamin D resistant rickets), familial hypophosphatemia and hypoparathyroidism, and in the management of hypocalcemia and renal osteodystrophy in patients with chronic renal failure undergoing dialysis. Also used in conjunction with calcium in the management and prevention of primary or corticosteroid-induced osteoporosis.
Vitamin D should not be given to patients with hypercalcemia or evidence of vitamin D toxicity. Use of vitamin D in patients with known hypersensitivity to vitamin D (or drugs of the same class) or any of the inactive ingredients is contraindicated. Calcitriol has been found to induce differentiation and/or inhibit cell proliferation in a number of malignant cell lines including human prostate cancer cells. Vitamin D deficiency has long been suspected to increase the susceptibility to tuberculosis.